The damage in this photo is
consistent with a low-end
EF1
tornado. It generally takes winds of 90 to 100 mph to cause a
well-constructed barn to collapse.

Related NWS Product:
Tornado WarningSafety Note: Poorly constructed structures such as barns and
outhouses are not safe places to be in a tornado. As seen here,
their lack of interior walls make them susceptible to collapse, which
can lead to serious injury or death. When a tornado warning is
issued, move to a sturdy building with a basement or small enclosed
rooms.